Abstract: Soil respiration is very important for global carbon budget, while the measurements once a day may cause biases in results. For detecting the deviations, and determining the best time for measuring soil respiration rates, simultaneous determinations of the diurnal dynamics of soil respiration, soil temperature and air temperature of four vegetation types (forest, shrub, grassland, meadow) and 13 community composition types in the Saihanba Forestry Center, Hebei Province, north China were made from June to August, 2011. It was found that soil respiration rates deviate -26%~68% from the average when measured at different times. Soil respiration rate was less affected by time of day in the forest, while 7:30?10:30 and 17:00?19:00 may be the best time for measurements in grassland and meadow (average deviation < 10%). The daily variations in soil respiration rates were closely correlated to that of soil and air temperature. This study suggests that soil respiration rates are affected by daily changes that cannot be ignored.

Key words: daily change, environmental factor, short-time measurement, soil respiration rates

摘要： 一天一次的土壤呼吸测定方式可能会引起结果的偏差, 为了估计这种偏差以及确定土壤呼吸测定的最适宜时间, 2011年6?8月在河北省塞罕坝地区开展4种植被类型(森林、灌丛、草原和草甸)、13个群落类型土壤呼吸速率日动态以及土壤表层10 cm温度和气温的同步测定。结果表明: 在一天内不同时间进行测定, 可导致土壤呼吸速率偏离程度在-26%~68%; 森林在一天内不同时间进行测定, 对土壤呼吸速率的影响较小(距离日平均值的偏离<10%); 草原和草甸通常在早上7:30-10:30和下午17:00-19:00进行测定对土壤呼吸速率的影响较小(距离日平均值的偏离<10%)。土壤呼吸速率的日变化与土壤温度和气温的日变化密切相关。研究表明, 如果忽略土壤呼吸的日动态, 将会对土壤呼吸速率的估算带来显著影响。

关键词: 日动态, 环境因子, 短期测定, 土壤呼吸速率